Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $228.33   5.661%   $241.2558   $241.26   $241.25   $241.30  
  Purchase #2 $22.35   5.862%   $23.6602   $23.66   $23.65   $23.70  
  Purchase #3 $79.48   8.623%   $86.3336   $86.33   $86.35   $86.30  
  Purchase #4 $80.55   7.632%   $86.6976   $86.70   $86.70   $86.70  
  Purchase #5 $183.89   11.462%   $204.9675   $204.97   $204.95   $205.00  
  Purchase #6 $207.40   13.183%   $234.7415   $234.74   $234.75   $234.70  
  Purchase #7 $185.31   3.281%   $191.39   $191.39   $191.40   $191.40  
  7 purchase totals = $987.31       $1,069.0462   $1,069.05   $1,069.05   $1,069.10